OK, so before you tie me up and burn me at a stake, let me try and explain. I have just finished reading Gerry Duggan's run on Uncanny Avengers. Great book, best of the 'Avengers' titles in my opinion. Anyway, there is a character called Synapse, the 'token' Inhuman of the team. During the book she bonds with Cable, and at the end he stats that Xavier would have loved to help her understand her powers, and she would have been one of his best students. That got me thinking, would X-Fans be accepting of an Inhuman joining the X-Men?
Personally speaking, I rather like the idea. I would not want the X-Men to no longer be mutant related, but this could be a good way in-universe to heal the schism between the two factions. They do share many similarities (No Marvel, that does not mean you can replace one with the other) and it would be an interesting way to see new Nuhuman characters who do not follow the ways of the Royal Family. Besides, haven't aliens joined the X-Men before anyway? Having the X-Men and Inhumans actually be allies would have been a much better way to push the forward in the MU, rather then starting a sickening race war between the two.
The only problem I see is that some X-fans... really hate the Inhumans, so may see this less as an interesting story technique and more an insult...